Many conventional spinal stabilization systems may be categorized as including interspinous support systems, laminar hook systems, longitudinal rod systems or some combination thereof. Interspinous support systems generally include a spacer disposed between and directly engaging adjacent spinous processes. The spacer may include seating surfaces that are contoured or configured to fittingly engage or receive the opposing spinous processes, thereby maintaining the axial and/or lateral disposition of the spacer relative thereto. Such interspinous spacers provide a support structure adapted to reduce or limit any reduction in the intervertebral spacing between the adjacent vertebrae. Typical laminar hook systems include one or more pair of hooks interconnected by a flexible cable or cord. The hooks, which are connected to opposing ends of the cable or cord, attach to the superior and inferior laminar edge regions of adjacent vertebrae. The flexible cords are then adjusted to the appropriate length such that the laminar hooks remain engaged with and limit the distraction of the adjacent vertebra. Typical longitudinal rod systems include one or more rods disposed along one or both sides of the interspinous processes of multiple vertebra of the spine. The longitudinal rods are fixed to the one or more of the vertebrae via fixation devices such as bone screws. Additionally, some longitudinal rod systems often include fasteners and/or plates fixing the longitudinal rods directly to the interspinous processes.
While multiple variations of the aforementioned spinal stabilization systems have been successfully implemented for correcting spinal alignment, relative shortcomings do exist. For example, interspinous spacer systems rely on direct engagement between adjacent interspinous processes. This system relies on a reactive moment applied directly to one or both of the spinous processes. Because of the configuration and location of the spinous processes relative to the remainder of the vertebra, the moment generated by these systems can potentially cause misalignment of the corresponding vertebrae relative to the rest of the spine. Thus, the systems often implement an additional component such as a flexible band and/or cord wrapped around the adjacent spinous processes to limit misalignment thereof. Additionally, such interspinous spacer systems, as stated above, directly abuttingly engage the spinous processes. Accordingly, the interspinous spacer systems rely on the integrity of the spinous processes, which can become brittle or unreliable due to aging or other factors.
One shortcoming of existing laminar hook systems is that such systems only serve to minimize distraction. Such systems, alone, are incapable of minimizing reduction of the intervertebral spacing. Additionally, laminar hook systems often include a flexible cord or cable. Such flexible cords, in certain situations, may actually serve to increase the reduction in the intervertebral spacing unless finely adjusted and/or loaded during implantation. Such fine adjustments can be deemed cumbersome and tedious by a surgeon. For example, in the system described above, the surgeon must first attach one hook upon an edge of a laminar region of a first vertebra, subsequently attach the second hook along an edge of a laminar region of a second vertebra, and finally adjust the tension in the interconnecting cord to insure the laminar hooks maintain engagement with the vertebra without, applying too great a compressive force that reduces the intervertebral spacing beyond a desired amount. Such steps in the surgery process require precision and accuracy and increase the time and cost of ultimately performing the operation.
Lastly, longitudinal rod systems, as mentioned above, require many components such as rods requiring alignment and screws that need to be threaded into vertebra during surgery. These systems are very cumbersome and expensive. Additionally, similar to the systems described above, such systems require ample precision and accuracy on the part of the surgeon, which ultimately increases operation time and cost.